Dot Physics

Gas prices may be trending down, but they are still quite high. How can we save gas? One of my colleagues suggested we can save gas by getting rid of all drive throughs. This means it is my job to estimate how much could be saved.

**Starting Assumptions (estimations)**

How many drive-throughs are there in the U.S.A.? When I think of drive-throughs, I think of McDonalds. [Wikipedia](http://en.wikipedia.org/wiki/Mcdonalds) says there are 31,000 restaurants world wide. I am going to say there are around 20,000 in the U.S. that have drive-throughs. So then, how many total drive-throughs? In my town, there are two McDonalds and probably 8 other major drive-throughs (Wendy’s, Burger King, Taco Bell etc….). This will give an extremely rough estimate of 100,000 drive-throughs in the U.S. (drive-through fast food).

There are also other kinds of drive-throughs. Drive-through banks, starbucks, pharmacy, liquor (yes, they exist). All of these will have different times, so I will first just deal with the fast food drive-throughs.

How many cars go through the drive-through a day and how long do they idle? I am going to estimate that the average over 8 hours a day is 2 cars in the drive-through line with an average wait time of 2 minutes. Yes, at lunch time there is a longer line, but sometimes there is no line. This is my estimation and I am sticking to it.

**Calculating the hours of idle time**

From this, I can calculate the average idle time. If there are 100,000 drive-throughs and for 8 hours there are two cars idling (I guess the wait time does not matter), that would be 1,600,000 idle-hours per day (100,000 x 8 hours x 2 cars). How much fuel does this use? Anecdotal claims from the internets say that cars use around 0.3 gallons per hour idling (I would have guessed higher than this). For this calculation, I will use 0.25 gallons of gas per hour idling. So, the total fuel per day wasted in drive-through (just restaurants) would be: 400,000 gallons.

**Comparing to the U.S. oil used per day**

Now to compare this to the 20 million barrels of oil used per day. 1 barrel of oil produces about 20 gallons of gasoline. So 400,000 gallons of gas saved would be 20,000 barrels of oil saved. This is just 0.1% of the oil used per day. Not nearly as much as the claimed 3% savings from tire pressure (although that is for people that don’t already have properly inflated tires). Also, that 3% is for individual savings, not for the whole nation.

**Slow Down**

I still think the best way to save oil is to drive slower.

Either way, the real issue is (as stated in the time article) how much would we get from off shore drilling? How much can we save by changing stuff.

Comments

  1. #1 offshore generic pharmacy
    December 23, 2008

    Great Post thanks for the information.

  2. #2 mssmotorrd
    May 3, 2009

    It’s the first time I commented here and I must say you share us genuine, and quality information for bloggers! Good job.
    p.s. You have a very good template for your blog. Where did you find it?

  3. #3 Rhett
    May 3, 2009

    mssmotorrd,

    I am using the wordpress theme Elegant Box 2.1.6 by mg12. Really, I just wanted something simple that had a white background so my equation pictures would show up fine. Glad you like the blog.

  4. #4 auction
    August 7, 2009

    Hi thanks for the information I do agree that there is a problem with too much fuel I think maybe the new petrol/electric cars are to way to go as the petrol engine turns off in the drive through

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